The invention relates to a method of visually positioning light conducting fibers. The invention also relates to a device for visually positioning light conducting fibers.
The method and device can be used to position the ends of two light conducting fibers with respect to each other and with respect to a heat source so that the fibers can be welded to each other. An example of such a method and device is described in an article by I. Hatakeyama, et al entitled "Fusion Splices for Single-Mode Optical Fibers" (I.E.E.E. Journal of Quantum Electronics, Vol. QE-14, No. 8, pages 614-619, August 1978). Since the light conduction in light conducting fibers takes place through the core, the orientation of the core is of importance during positioning. In the known welding apparatus, however, it is common practice to illuminate the claddings of the fibers and to observe the claddings by means of, for example, a microscope or a projection system. When the core is arranged eccentrically to the outer circumference of the cladding, positioning errors result. These errors may lead to unacceptably large light losses in the weld, especially when monomode fibers are welded.
This disadvantage can be overcome by illuminating one fiber and measuring the quantity of light emanating from the second fiber. When this quantity of light is at a maximum, the cores of the fibers at the area of the weld are positioned correctly.
Another method, in which the light conducted through the core and emanating at an end of the fiber is observed, can be used when an end of a light conducting fiber has to be mounted in an envelope. The surface of the envelope will serve later on as a reference surface for automatically bringing the core of the fiber to the desired position in, for example, an optical connector. An example thereof is described in U.S. Pat. No. 4,289,374.
A similar method can also be used when a fiber end must be arranged in the correct position with respect to a lens, as described in U.S. Pat. No. 4,451,115 (corresponding to Dutch Patent Application No. 7905610). However, all these methods are impractical because in order to introduce the light into the core, the other end of the fiber must be illuminated. This end may be kilometers away from the splice.